Abstract

Purpose: An averaging of retina scans is integrated in the algorithm of most Optical Coherence Tomography (OCT) devices to improve final image quality. This study aimed to evaluate image modification or alteration induced by this averaging. Methods: Thirty-three consecutive patients examined with the Opko®, SLO/OCT OTI were included in this retrospective study. Final OCT-B images were built with an averaging of 20 OCT-B Scans. Fifteen of these patients were followed for the monitoring of antimalarials while the 18 others were followed up for various retina conditions. Final OCT-B images were decomposed into their Scan 1, Scan 5 and Scan 10. Based on the Scan 1 image, we evaluated changes on 4 items (i) Choroid, (ii) Retinal Pigment Epithelium (RPE) and or Ellipsoid zone (EZ), (iii) Neuroretina, and (iv) Anterior profile line. The items were noted 0 or 1 (absence or presence of subtle alteration). We then compared the percentages of alterations for Scan 5, Scan 10 and Scan 20. For the 15 patients treated with antimalarials, based on clinical evaluation, visual field, multifocal electroretinogram, fundus autofluorescence and on the presence of alteration of the outer retinal layers on OCT the patients were separated into group (A) : no sign of antiamarials intoxication (n = 7) and group (B) : presence of antiamarials intoxication (n = 8). Results: All the images of the 33 patients included in this series were used for the analysis. Subtle alterations with loss of some details (retina vessels and their shadows, exudates, choroid lobules) were observed along with increased averaging. For the whole series, with 4 items × 33 patients (132 items) we noticed 24 changes on Scan 5 (18.18%), 44 changes on Scan10 (33.33%), and 47 changes (35%) on Scan 20. For the 15 patients with antiamarials, on Scan 10 and Scan 20, image modification was more frequent in the group with intoxication (75%) than in the group without intoxication (42.8%). Conclusion: For OCT devices with technical characteristics similar to the Opko® and for patients with fixation characteristics similar to those of our series, it would be worth discussing the possibility of image alteration induced by scan averaging if Scan 10 or above images are used. For current OCT devices, as the number of scans averaged has now increased, our data suggest that acquisition speed, better co-localization of repeated OCT Scans and other technical improvements could influence the benefit/loss ratio of averaging.

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